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Continuous nerve block assemblyRelated Patent Categories: Surgery, Means For Introducing Or Removing Material From Body For Therapeutic Purposes (e.g., Medicating, Irrigating, Aspirating, Etc.), Infrared, Visible Light, Ultraviolet, X-ray Or Electrical Energy Applied To Body (e.g., Iontophoresis, Etc.)Continuous nerve block assembly description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080058702, Continuous nerve block assembly. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATION [0001] The present patent document is a continuation-in-part of application Ser. No. 11/635,931, filed Dec. 8, 2006, which claims the benefit of the filing date under 35 U.S.C. .sctn.119(e) of Provisional U.S. Patent Application Ser. No. 60/749,664, filed Dec. 12, 2005. Each of the foregoing applications is hereby incorporated by reference. BACKGROUND [0002] 1. Technical Field [0003] The present invention relates generally to an assembly for use in blocking a peripheral nerve of a patient to produce regional anesthesia. More particularly, the invention relates to an echogenic continuous nerve block assembly suitable for such use. The invention further relates to a method for continuously blocking a nerve. [0004] 2. Background Information [0005] It is a well known medical practice to produce regional anesthesia in a patient by depositing a local anesthetic along the path of one or more peripheral nerves. The success of the technique is largely dependent upon the ability of the clinician to deposit the anesthetic in close proximity to the nerve. Local anesthetics comprise a class of drugs which reversibly interact with a nerve in a manner such that the propagation of signals along the nerve fiber is significantly reduced, or stopped altogether, for a limited period of time. When such drugs are deposited along large nerve trunks, such as the femoral nerve in the groin or the nerve trunk of the brachial plexus in the axilla or neck, the effect is to make the targeted body structure, such as a body limb, insensate or "numb." [0006] When the local anesthetic is intended to be injected into the groin, neck or axilla, the relevant nerve or nerves must, of course, be located before the injection is given. A general understanding of surface anatomy allows the general area of the nerve to initially be located. Historically the nerve was located by eliciting a paraesthesia, or pain, resulting from the needle coming into contact with the nerve fiber. This is very similar to the sensation experienced by hitting the "crazy bone", where the ulnar nerve is stimulated by pressure being placed on it between the skin and the bone. When this process is done with a needle, the risk of damaging a nerve fiber is high, with the possible result of permanent nerve injury. This technique has been largely abandoned due to the high possibility of such permanent injury. [0007] The use of nerve blocks to accomplish such anesthesia has now progressed to the point where a stimulating needle may be utilized to locate a nerve, without making direct contact with the nerve. Nerve block systems are provided with certain features to minimize damage to the nerve. A first feature is to utilize a beveled needle end cut at an angle. Typically, such needles are provided to have tip angles of about 15.degree., 30.degree. or 45.degree.. A more blunt needle allows the user to feel the tissue during insertion, and is less likely to cause damage to the nerve. A second feature is to provide the needle with a coaxial design, consisting of a needle shaft covered with a plastic coating, such as PTFE. The needle shaft is connected to an electrode, and the needle electrode system and a grounding skin electrode are connected to a commercially available nerve stimulation box. [0008] An electrical circuit is formed when the needle is placed in the patient's tissue and the grounding electrode is connected to the patient's skin, e.g., with a conventional EKG electrode. The nerve stimulation resulting from this circuit is capable of delivering adjustable pulses of electrical energy through the needle. When the needle tip is in close proximity to the nerve, the motor nerve fibers are stimulated to cause muscles innervated by the nerve to twitch by electrical stimulation resulting from the electrical current flow in the electrical circuit. This mechanism is similar to that observed in a high school biology experiment, when the leg of a freshly dead frog is made to twitch by direct electrical stimulation of the nerve, thereby innervating the leg. In this nerve stimulation technique, the clinicians are, in effect, attempting to localize the nerve without actually puncturing the nerve tissue. The technique is intended to allow the needle to come close to the nerve, without actually contacting the nerve fibers in a manner that might cause damage to the nerve. [0009] Needle insertion by the aforementioned technique is based upon clinical judgment, and therefore, is not precise. The amount of electric current necessary to make the correct muscle twitch for the nerve to be blocked is determined by the proximity of the needle to the nerve. Generally, only a small amount of current is required, since resistance is typically minimal as the needle approaches the nerve. In clinical practice, this is typically performed at 1 to 4 Hz stimulation frequency, with an optimal current of 0.5 milliamps or less to bring the needle in close enough proximity to the nerve for drug injection. The actual voltage required is proprietary, and is a property of the particular peripheral nerve stimulator utilized in the technique. It is set at a value to produce a motor response without pain. A limitation of this technique is that it is a blind technique that is carried out based on a general understanding of the surface anatomy of the particular nerve to be blocked, and without a precise location of the nerve under the skin. [0010] Ultrasound energy comprises high frequency sound waves generated in the 2 to 15 MHz range. In common medical practice, a range of 5 to 12 MHz is employed for most applications, as this range provides optimal tissue resolution and penetration. The sound waves are commonly generated using a piezoelectric crystal. Piezoelectric crystals produce ultrasound energy when electrically stimulated, and also respond to reflected ultrasound energy. The ultrasound energy is pulsed and time locked. Ultrasound energy is typically reflected, and this reflected ultrasound energy is capable of amplification. Measuring reflected amplified energy enables the clinician to determine a range or distance to a tissue interface. Medical ultrasound techniques, such as 2D medical ultrasound, typically employ a piezoelectric effect reflective head, a computer, an electronic component, and a monitor to display the anatomy generated by the ultrasound integration of the tissue being examined. [0011] A 2D ultrasound technique typically uses an ultrasound head with a set of piezoelectric crystals in alignment, which crystals can be electronically switched on or off to respond to reflected ultrasound energy. The time delay between ultrasound emission and reflection can be used to construct a 2D picture of the tissue in alignment in the ultrasound plane generated. When the piezoelectric crystals are switched on and off electronically, a planar picture of the anatomy is created and displayed on the 2D ultrasound monitor. The 2D ultrasound machine allows tissue and anatomy to be visualized in both the axial and lateral direction. By controlling the switching order and timing of the individual piezoelectric crystals in the ultrasound head, the tissue can be scanned in a temporal fashion, thus creating a real time display of the tissue, and thus motion. [0012] Ultrasound techniques, such as 2D ultrasound, are widely used in modern medicine. Such techniques are currently used for peripheral nerve blockage by allowing the clinician to view the nerve to be blocked in real time. In using a 2D ultrasound machine to block a nerve, the clinician is able to see below the skin, and thereby view the location of the nerve or nerves to be blocked. This renders greater precision in the procedure, and allows the clinician to advance the needle to the desired position relative to the nerve. A local anesthetic can then be deposited near the nerve to be blocked. [0013] Conventional nerve stimulating block needles are typically of coaxial design. These needles have an inner needle portion made of metallic material, typically surgical grade steel. A plastic matrix covers most of the length of the needle, and extends generally from the proximal end of the needle nearly to the bare metal needle tip. This type of needle construction ensures maximal current density, as the current can only exit at the unencased metal needle tip. The plastic covering of the needle insulates the remaining portion of the needle from the remaining patient tissue, ensuring that electrical current primarily exits at the needle tip. The needle tip, when in close proximity to the nerve, localizes the nerve with electrical stimulation while minimizing nerve damage. [0014] One major shortcoming of the 2D ultrasound technique is that the needle is often not easily visible in the plane of the 2D ultrasound beam. Maximum reflection of ultrasound energy occurs when the needle is at a 90.degree. angle to the direction of the ultrasound waves in the 2D ultrasound plane. The signal degrades as this angle is reduced, to a point at which the needle becomes invisible in the 2D ultrasound plane. As a result, it is often ergonomically difficult to align the needle with or under the ultrasound head, define the tissue anatomy, and advance the needle in a 3D structure, while keeping the needle in view on the narrow 2D ultrasound plane. [0015] When regional anesthesia is produced in a patient by injecting the local anesthetic along the path of a peripheral nerve utilizing a needle, the anesthesia is generally effective to make the target nerve insensate for a relatively short period of time. This time period is typically a matter of hours, the exact period depending upon the particular anesthetic used, and the specific dosage of the anesthetic injected into the patient. In some surgical procedures, however, it is desired to provide continuous introduction of anesthetic, such that the period of insensitivity can be extended beyond that which is safely available from a single injection, such as for a period of several days. In such cases, multiple, spaced doses may be injected into the patient to provide continuous analgesia. The use of multiple injections may be traumatic to the patient, and also requires the technician to locate multiple suitable injection sites on the skin of the patient. As an alternative, a catheter may be inserted through the barrel of the needle, which catheter is in fluid communication with a source of anesthetic. An infusion pump can be used to continuously pump anesthetic through the catheter to the target site for the designated period of time. However, when techniques such as 2D ultrasound are utilized, the distal tip of the catheter may not be visible under ultrasound. As a result, it can be difficult to determine whether the distal tip of the catheter has been optimally placed relative to the nerve. [0016] It would be desirable to provide a nerve block assembly that utilizes an injection needle for an anesthetic, which needle is capable of simultaneous nerve stimulation and ultrasound visualization. It would also be desirable to include a catheter within the assembly capable of transmitting an anesthetic to a target site for continuous nerve block. BRIEF SUMMARY [0017] The present invention addresses the limitations of the prior art. An assembly is provided for continuous blockage of a nerve of a patient. The assembly includes a needle comprising a hollow needle conduit having a shaft portion and a tip portion, a generally non-conductive layer disposed along a length of the conduit shaft portion, and an echogenic surface extending along at least a portion of the needle. A catheter is sized to be received in the shaft portion of the needle. The catheter shaft has a bore extending at least partially therethrough for transmittal of an anesthetic to a vicinity of the nerve. The catheter has an echogenic capability, such as an echogenic surface disposed along a portion of its length. The needle is capable of providing electrical stimulation to the nerve, and the respective needle and catheter echogenic surfaces are arranged for enhancing a reflection of ultrasound waves generated during ultrasound visualization. [0018] In another form, the invention comprises a method for continuous blocking of a nerve of a patient. A hyperechoic stimulating block needle comprises an electrically conductive hollow needle conduit having a shaft portion and a distal tip, a generally non-conductive layer extending along the conduit shaft portion, and an echogenic surface extending along at least a portion of the length of the needle. The needle tip is inserted into a patient in a vicinity of the nerve, and the tip is aligned in proximity with the nerve by visualization with ultrasonic imaging and by electrical nerve stimulation. A catheter is passed through the hollow needle conduit such that a distal end of the catheter extends distally beyond the needle tip. The catheter distal end has an echogenic surface that enables the distal end of the catheter to be aligned in proximity with the nerve by ultrasonic imaging. Continuous, spaced, doses of an anesthetic suitable for blocking the nerve are injected into the patient through the catheter. [0019] In still another form, the invention comprises an echogenic catheter suitable for ultrasonic visualization during a medical procedure. The catheter comprises a catheter shaft having a proximal end, a distal end, and a bore extending at least partially through the shaft. The catheter shaft is formed from a generally flexible polymeric composition, such as a urethane or a nylon composition. A coiled ribbon is wrapped around at least a distal portion of the catheter shaft. The coiled ribbon, preferably formed from a metal or a metal alloy, includes deformations shaped and positioned along a surface of the ribbon to reflect ultrasound waves, so that the ribbon is visible under ultrasonic visualization. BRIEF DESCRIPTION OF THE DRAWINGS [0020] FIG. 1 illustrates a perspective view of a hyperechoic stimulating block needle according to one embodiment of the present invention; Continue reading about Continuous nerve block assembly... 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